In the present 4G standard process, multiple-input multiple-output system (MIMO) technology is always considered as a key technology. Introduction of multiple antennas enable the system to achieve higher diversity gain and multiplexing gain, thereby greatly increasing spectrum efficiency of the communication system and capacity of communication channels and the system. MIMO system includes single-user multiple-input multiple-output system (SU-MIMO) and multiple-user multiple-input multiple-output system (MU-MIMO). In MU-MIMO, different user's data can be transmitted in the same time-frequency resource block, thus increasing data transmission rate, however, there are interferences among multiple users. Currently, in order to get multi-user gain in MU-MIMO and eliminate the interferences among multiple user terminals, some methods are usually adopted, such as user terminals feedback Channel State Information (CSI) to enable a transmitting-end pre-coding and multiple users scheduling strategy. In recently published articles, a solution named as MAT scheme is provided.
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The above solution can enhance degree of freedom (DoF) by using outdated Channel State Information. The article concludes a result by using the outdated Channel State Information which is fed back: in a MU-MIMO system with K transmitting antennas and K single-antenna users, the greatest degree of freedom can be gotten is: DoF=K/(1+½+⅓+ . . . +1/K)>1. As shown in the above table, Comparison are performed for different K values.
But for a K×K MU-MIMO system, if the MAT scheme is adopted, there will be problems that signal transmission delay of the multiple user multiple input multiple output system where a channel changes rapidly is too long, where the delayed time gets longer with increasing of the amount of antennas, and no extra gain of the system can be gotten by using spare antennas. There is no valid solution for the above problems in the prior art.